CN112080109A

CN112080109A - Preparation method of multidimensional special-shaped high-transparency high-scattering environment-friendly formaldehyde-free wood-based composite material

Info

Publication number: CN112080109A
Application number: CN202010907668.XA
Authority: CN
Inventors: 唐启恒; 郭文静; 任一萍
Original assignee: Research Institute of Forestry New Technology of Chinese Academy of Forestry
Current assignee: Research Institute of Forestry New Technology of Chinese Academy of Forestry
Priority date: 2020-09-02
Filing date: 2020-09-02
Publication date: 2020-12-15
Anticipated expiration: 2040-09-02
Also published as: CN112080109B

Abstract

The invention relates to a preparation method of a multi-dimensional special-shaped high-transparency high-scattering environment-friendly aldehyde-free wood-based composite material, belonging to the field of preparation of high-scattering materials and optical illumination. The method comprises the steps of removing lignin from wood fibers, uniformly paving the wood fibers into a three-dimensional fluffy fiber net, putting the three-dimensional fluffy fiber net into a female die of a multi-dimensional special-shaped die, closing a male die, then penetrating transparent liquid resin into the wood fibers, and carrying out curing treatment, wherein the resin is a non-polar material, the wood fibers are polar materials, and the interface compatibility between the wood fibers and the polar materials is poor, so that interface gaps are formed, light is promoted to be seriously scattered in the composite material, and the multi-dimensional special-shaped high-transparency high-scattering environment-friendly formaldehyde-free wood-based composite. The preparation method is simple and easy to implement, low in production cost and environment-friendly, and the prepared product has good light transmittance and scattering property.

Description

Preparation method of multidimensional special-shaped high-transparency high-scattering environment-friendly formaldehyde-free wood-based composite material

Technical Field

The invention relates to a preparation method of a high-scattering material, in particular to a preparation method of a multi-dimensional special-shaped high-transparency high-scattering environment-friendly aldehyde-free wood-based composite material, and particularly relates to a novel high-haze material which generates pores in a medium due to incompatibility of interfaces caused by polarity difference between wood fibers and resin and causes light scattering due to the fact that the size of the pores is far larger than one tenth of the wavelength of light, belonging to the field of preparation of high-scattering materials and optical illumination.

Background

In recent years, with the rapid development of science and technology, the demands for road lighting and brightening engineering are gradually increased. Generally, a lighting lamp, an indicator light, a billboard, a display window, a fluorescent tube and other devices need to be provided with a lighting lampshade, and the lampshade needs to have high transparency and high scattering functions. The composite material containing the two functions can not only allow light to penetrate through, but also uniformly scatter incident light to different directions, and reduce dizziness and discomfort caused by light transmission. The method for preparing the high-transparency material is simple, and can be achieved by only adopting resin with good transparency as a base material, but in order to achieve the purpose of high scattering, various methods are needed to enable light rays in the composite material to be transmitted towards different directions.

Scattering principle of light: when light passes through the inhomogeneous medium, the vibration electric field of the light wave makes the electrons in the particles produce forced vibration, the particles become secondary wave source and emit electromagnetic wave in all directions, and the light beam is partially deviated from the incident light direction, so that light intensity may be observed in other directions. According to the scattering principle, a special microstructure is endowed on the surface of a transparent base material or a light scattering agent is added into the base material to respectively prepare a surface scattering material and a bulk scattering material.

The surface scattering material can accurately design and prepare a scattering center, one surface (generally an inner surface) of a transparent plate or other-shaped product is polished, the corresponding surface of a coating or a forming mould of the transparent plate or other-shaped product is subjected to sand blasting or indentation treatment, and the rough surface of the transparent plate or other-shaped product is utilized to generate light scattering. The bulk scattering material is composed of a matrix material and a scatterer material, most commonly is a high scattering material taking transparent polymers such as polycarbonate, polyethylene terephthalate, polystyrene, polymethyl methacrylate and the like as a matrix, and the scatterer mainly comprises inorganic scattering particles, organic scattering particles, composite scattering particles and polymer scatterers. A large number of patents currently disclose that inorganic materials such as silicon oxide, titanium oxide, barium sulfate, and calcium carbonate are mixed into a polycarbonate resin matrix as a scattering agent, but due to the incompatibility of the inorganic materials and the polycarbonate interface, the addition of inorganic fillers may cause the degradation of the mechanical properties of the polycarbonate resin, which may affect the subsequent use problems. For example, patents JP03078701 and JP05257002 disclose the preparation of light scattering plates by adding silica as scattering particles to polycarbonate. In addition, the bulk scattering material also comprises polycarbonate composite light scattering material which takes conventional polymer as a scattering body. CN102702713A describes a scattering material using a conventional polymer as a scatterer. Polycarbonate resin is used as a matrix material, and polymers which can be melted and deformed in the polycarbonate processing and forming process, such as acrylonitrile copolymer, are used as scatterer materials.

In the existing preparation method of the light scattering material, no matter the light scattering material is surface scattering material or bulk scattering material, the propagation direction of light is changed mainly by adjusting the size of a medium surface or an internal fine nano structure, so that light is subjected to Mie scattering or other resonance scattering effects.

Currently, surface scattering materials require polishing, coating or sandblasting or scoring of the corresponding surface of the article to be molded, and use their rough surfaces to produce light scattering. The bulk scattering material is composed of a matrix material and a scatterer material, and the scatterer mainly comprises inorganic scattering particles, organic scattering particles, composite scattering particles and polymer scatterers. In the existing preparation method of light scattering, no matter surface scattering or bulk scattering materials are adopted, the propagation direction of light is changed mainly by adjusting the size of a medium surface or an internal fine nano structure, so that light is subjected to Mie scattering or other resonance scattering effects. Thus, this technique is costly, multiple steps, cumbersome, and exhibits limited capabilities for large-scale commercial applications.

Disclosure of Invention

The invention aims to provide a preparation method of a novel wood-based composite material, which is simple and easy to implement, low in production cost, green and environment-friendly and has good light transmittance and scattering performance. The structure based on the scatterer has great influence on the scattering effect of the light scattering material, and the invention prepares the light scattering particles with special structures by adopting a simple and efficient method so as to obtain the high-performance light scattering material, thereby providing an attempt for the future development of the high scattering material.

The wood fiber is a natural degradable and renewable material and is an opaque material. On a microscopic scale, the lignocellulosic cell wall can be viewed as a composite material with lignin and hemicellulose as the matrix and cellulose as the reinforcing phase. Dissolving lignin and an extract which have the capacity of absorbing visible light in the wood fiber to obtain white lignin-removed wood fiber consisting of cellulose (the refractive index is 1.53) and hemicellulose (the refractive index is approximately 1.53), and then permeating transparent resin matched with the refractive index into wood fiber cells to prepare the wood composite material with high light transmittance. Furthermore, the resin is a non-polar material, while the wood fiber is a polar material, and the interface is incompatible due to the polarity difference between the resin and the wood fiber, so that pores inside the medium are generated, and the pore size is far larger than one tenth of the wavelength of light, so that the light is scattered to form the novel high-scattering material, and the high-scattering material can be prepared without processing the surface of the material or adding any scatterer inside the material.

At present, the application of wood is mainly in the traditional fields of artificial boards and the like, and the added value is low. The development of the novel high-transparency high-scattering environment-friendly formaldehyde-free wood-based composite material not only can prepare the wood-based composite material with good light transmittance and scattering performance, promote the development of degradable materials in the high-scattering material, but also can apply the transparent wood to high-tech fields such as photoelectron and the like, and improve the high value-added utilization of the wood.

The above object of the present invention is achieved by the following technical solutions:

a preparation method of a multi-dimensional special-shaped high-transparency high-scattering environment-friendly aldehyde-free wood-based composite material comprises the following steps: removing lignin from wood fibers, uniformly paving the wood fibers into a three-dimensional fluffy fiber net, putting the three-dimensional fluffy fiber net into a female die of a multi-dimensional special-shaped die, closing a male die, then permeating transparent liquid resin into the wood fibers (including the interior of the wood fibers and between the fibers), and carrying out high-temperature curing treatment.

The preparation method comprises the following specific steps:

(1) removing lignin: soaking the wood fiber in sodium hypochlorite or sodium chlorite or a mixed aqueous solution of the sodium hypochlorite and the sodium chlorite, raising the temperature of the aqueous solution to 70-100 ℃, stopping heating when the mass content of lignin in the wood fiber is less than or equal to 10%, cleaning the wood fiber by using clear water until the aqueous solution is neutral, and finally drying the wood fiber; the diameter of the wood fiber is less than or equal to 50 mu m, and the length of the wood fiber is less than or equal to 2 mm;

(2) paving a fiber net: paving the aired lignocellulose into a three-dimensional uniformly-interwoven fiber net, and then putting the fiber net into a multi-dimensional special-shaped mold;

(3) resin infiltration: and (2) permeating the resin into the fiber web by adopting a VARTM (vacuum assisted resin transfer molding) or HT-RTM (high pressure resin transfer molding) or VARI (vacuum assisted molding) process, curing the resin at a certain temperature (20-200 ℃) until the curing reaction is finished, removing the mold, and taking out the cured sample to obtain the high-transparency high-scattering composite material.

In the step (1), the length of the wood fiber is preferably as follows: the fiber with the length less than or equal to 0.15mm accounts for more than 60 percent of the total fiber mass fraction, and the following is more preferable: the fiber with the length less than or equal to 0.10mm accounts for more than 90 percent of the total fiber mass fraction.

When the lignin of the wood fiber is removed, the water boiling time is 10min-5h, based on the condition that the wood fiber is just submerged by sodium hypochlorite or sodium chlorite or a mixed aqueous solution of the sodium hypochlorite and the sodium chlorite in a container. The mass fraction of the aqueous solution of sodium hypochlorite, sodium chlorite or a mixture of the sodium hypochlorite and the sodium chlorite is not particularly limited, and is preferably 1 to 15 percent, more preferably 3 to 10 percent; the water boiling time is preferably 30min-2 h. In the mixed aqueous solution of sodium hypochlorite and sodium chlorite, the mass ratio of the sodium hypochlorite to the sodium chlorite can be any, and the preferred mass ratio is 1:1-2: 1.

In the step (2), the paving is not particularly limited, and the paving is preferably performed by hand or by air flow or by a carding machine to form a three-dimensional fluffy network, and more preferably by air flow.

The manual paving is to manually scatter the fibers by hand and then manually and uniformly lay the fibers in a mold; the air flow paving or carding paving is to open the aired wood fiber, then uniformly lay the wood fiber into a three-dimensional fluffy network shape by means of air flow or a carding machine, and then cut into a proper size according to the size of the mould and lay the wood fiber in the middle of the mould.

The multi-dimensional special-shaped mould comprises various moulds such as a square block mould, a rectangular block mould, a helmet mould, a lampshade mould, a hemisphere mould and the like.

In the step (3), the resin is an epoxy resin system, polymethyl methacrylate or polyurethane.

In the permeation process, the viscosity of the resin is less than or equal to 10Pa · s.

The epoxy resin system is a mixture of epoxy resin monomers and a curing agent, the curing agent is polyamide, anhydride, diamine or polyamine substances, and the curing agent accounts for 5-40% of the total mass; the curing temperature is 20-200 ℃, and the light transmittance after curing is more than or equal to 85 percent.

The curing temperature of the polymethyl methacrylate is 50-100 ℃, and the transmittance after curing is more than or equal to 85%.

The polyurethane is obtained by carrying out polymerization reaction on raw materials of isocyanate, a polyglycol compound B and a chain extender, wherein the mass of the isocyanate and the chain extender accounts for less than 40% of the total mass of the polyurethane, the mass fraction of the isocyanate is less than or equal to 35%, and the mass fraction of the chain extender is less than or equal to 5%. The process conditions of the polymerization reaction are as follows: reacting isocyanate and polyglycol compound at 50-100 deg.c for 0.5-5 hr, adding chain extender, fast stirring to form molten polyurethane system, permeating wood fiber, and reacting at 50-150 deg.c for 1.5-10 hr.

The isocyanate is any one of diphenylmethane diisocyanate, isophorone diisocyanate and hexamethylene diisocyanate, the polyglycol compound B is any one of polytetrahydrofuran ether glycol, polyoxyethylene glycol, polytetrahydrofuran-ethylene oxide glycol and polyoxypropylene glycol, the number average molecular weight is 500-1500, and the chain extender is 1, 4-butanediol or 1, 3-butanediol or a mixture of the two in any proportion.

The curing temperature of the polyurethane is 50-150 ℃, and the transmittance after curing is more than or equal to 85%.

By adopting the VARTM or HT-RTM or VARI process, the resin is promoted to completely permeate into wood fiber network, especially wood fiber cell gaps, so that the internal porosity of the composite material after molding is less than or equal to 1 percent.

The VA-RTM is to inject an epoxy resin system, polymethyl methacrylate or polyurethane under the vacuum degree of less than or equal to 0.05MPa and the injection temperature of 20-50 ℃; the HT-RTM is to inject an epoxy resin system, polymethyl methacrylate or polyurethane under the injection pressure of more than or equal to 0.8MPa and the injection temperature of 20-50 ℃; the VARI is that epoxy resin system, polymethyl methacrylate or polyurethane is injected under the vacuum degree of less than or equal to 0.05MPa and the injection temperature of 20-40 ℃.

In the resin infiltration process, the mass fraction of the wood fiber reaches 75-90%, and the mass fraction of the resin matrix reaches 10-25%. The infiltration process is not particularly limited, and a preferred infiltration process is HT-RTM. The mass fraction of the wood fibres in the composite material is preferably 75-90%, more preferably 80-90%.

The method removes lignin of wood fiber, paves the wood fiber into a three-dimensional and uniformly interwoven fiber mesh in a female die of a multi-dimensional special-shaped die, adopts a VARTM (vacuum transfer molding) or HT-RTM (high-temperature-resin transfer molding) or VARI (vacuum-assisted injection molding) process to permeate resin into the fiber mesh, and then cures the resin at high temperature to obtain the high-transparency high-scattering environment-friendly formaldehyde-free wood-based composite material. The preparation method is simple and easy to implement, low in production cost and environment-friendly, and the prepared product has good light transmittance and scattering property.

The invention mainly utilizes the lignin-removed wood fiber and the transparent resin to be compounded, the polarity difference between the lignin-removed wood fiber and the transparent resin causes the interface to be incompatible, thereby generating the internal pores of the medium, and the pore size is far larger than one tenth of the optical wavelength to cause the light to be scattered, thereby preparing the high scattering material without processing the surface of the material or adding any scatterer in the material. The preparation method is simple and low in cost, not only promotes the development of the degradable material in the high-scattering material, but also can apply the transparent wood to the high-tech fields such as photoelectron and the like, and improves the high value-added utilization of the wood.

Drawings

FIG. 1 is a diagram of the process of delignification of wood fibers to pure white in example 1 of the present invention.

Fig. 2 is a flow chart of a method for preparing a high-transparency high-scattering environment-friendly aldehyde-free wood-based composite material by adopting a VARI process in example 1 of the present invention.

Fig. 3 shows the light transmittance of the high-transparency high-scattering environment-friendly aldehyde-free wood-based composite material in example 1 of the present invention.

Fig. 4 is a haze of the high-transparency high-scattering environment-friendly aldehyde-free wood-based composite material of example 1 of the present invention.

Fig. 5 is a bending strength graph of the high-transparency high-scattering environment-friendly aldehyde-free wood-based composite material in example 1 of the present invention.

Fig. 6 is a bending elastic modulus graph of the highly transparent, high scattering, environment-friendly and aldehyde-free wood-based composite material in example 1 of the present invention.

FIG. 7 shows the impact strength of the high-transparency, high-scattering, environment-friendly and aldehyde-free wood-based composite material in example 1 of the present invention.

Detailed Description

The invention evenly paves the lignin-removed wood fiber into a female die of a multidimensional special-shaped die to form a three-dimensional fluffy network, closes the male die, then permeates transparent liquid resin into the wood fiber (including the interior of the wood fiber and between fibers), and cures at a certain temperature. The resin-based non-polar material and the wood fiber-based polar material have poor interface compatibility, so that an interface gap is formed, light is promoted to be seriously scattered in the composite material, and the multi-dimensional special-shaped high-transparency high-scattering environment-friendly aldehyde-free wood-based composite material is obtained.

The preparation method specifically comprises the following steps:

(1) removing lignin: soaking the wood fiber in sodium hypochlorite or sodium chlorite or a mixed aqueous solution of the sodium hypochlorite and the sodium chlorite, raising the temperature of the aqueous solution to 70-100 ℃, stopping heating when the mass content of lignin in the wood fiber is less than or equal to 10%, cleaning the wood fiber by using clear water until the aqueous solution is neutral, and finally drying the wood fiber. The diameter of the wood fiber is less than or equal to 50 mu m, the length of all the fibers is required to be less than or equal to 2mm, and the mass fraction of the fibers with the length of less than or equal to 0.15mm in the total fiber is more than 60%. The wood fiber length is preferably: the mass fraction of the fibers with the length less than or equal to 0.15mm in the total fibers is more than or equal to 60 percent, and the mass fraction of the fibers is more preferably as follows: the mass fraction of the fibers with the length less than or equal to 0.10mm in the total fibers is more than or equal to 90 percent. Removing lignin by boiling sodium hypochlorite, sodium chlorite or their mixture in water for 10min-5 hr.

(2) Paving a fiber net: the aired lignocellulose is paved into a three-dimensional and uniformly interwoven fiber net, and then the fiber net is placed into a multi-dimensional special-shaped mold. The paving is carried out by adopting manual paving or air flow paving or carding machine paving to form a three-dimensional fluffy network shape. The multi-dimensional special-shaped mold comprises various molds such as a square mold, a helmet mold, a lampshade mold and a hemisphere mold. The manual paving is to manually scatter the fibers by hand and then manually and uniformly lay the fibers in a mold; the air flow paving or carding paving is to open the aired wood fiber, then uniformly lay the wood fiber into a three-dimensional fluffy network shape by means of air flow or a carding machine, and then cut the wood fiber into a proper size according to the size of the mold to be paved in the middle of the mold.

(3) Resin infiltration: and (3) permeating resin into the fiber mesh by adopting a VARTM (vacuum transfer molding) or HT-RTM or VARI (vacuum-assisted vacuum infiltration molding) process, curing the resin at high temperature until the curing reaction is finished, removing the mold, and taking out the cured sample to obtain the high-transparency high-scattering composite material. Wherein the content of wood fiber reaches 75-90%, and the content of resin matrix reaches 10-25%.

The resin is epoxy resin, polymethyl methacrylate or polyurethane. The viscosity of the resin is less than or equal to 10 Pa.s in the permeation process; the epoxy resin is a mixture of epoxy resin monomer and curing agent, the light transmittance after curing is more than or equal to 85 percent, and the high temperature is 20-200 ℃; the curing temperature of the polymethyl methacrylate is 50-100 ℃. Polyurethane, wherein the isocyanate is any one of diphenylmethane diisocyanate, isophorone diisocyanate or hexamethylene diisocyanate, B is any one of polytetrahydrofuran ether glycol or polyethylene oxide glycol or polytetrahydrofuran-ethylene oxide glycol or polypropylene oxide glycol, and the number average molecular weight is 500-1500; the chain extender is 1, 4-butanediol or 1, 3-butanediol or a mixture of the two; the curing temperature is 50-150 ℃; the mass of the isocyanate and the chain extender accounts for less than or equal to 40 percent of the mass of the total polyurethane.

The VARTM or HT-RTM or VARI process is to promote the resin to completely permeate into the wood fiber network, especially the wood fiber cell gap, so that the internal porosity of the composite material after molding is less than or equal to 1 percent.

VA-RTM: the vacuum degree is less than or equal to 0.05MPa, and the epoxy resin system, the polymethyl methacrylate system or the polyurethane system is injected at the injection temperature of 20-50 ℃.

HT-RTM: the injection pressure is not less than 0.8MPa, and the injection temperature is 20-50 ℃ and the epoxy resin system, the polymethyl methacrylate system or the polyurethane system is injected.

VARI: the vacuum degree is less than or equal to 0.05MPa, and the epoxy resin system, the polymethyl methacrylate system or the polyurethane system is injected at the injection temperature of 20-40 ℃.

Example 1:

a preparation method of a multi-dimensional special-shaped high-transparency high-scattering wood-based composite material comprises the following steps:

1) soaking 100 g of wood fiber (the fiber diameter is less than or equal to 50 mu m, the fiber length is less than or equal to 0.15mm and accounts for 60 percent of the total fiber mass) of poplar into a sodium chlorite aqueous solution (the sodium chlorite mass fraction is 4 percent), just submerging the fiber by the aqueous solution, raising the temperature of the aqueous solution to 100 ℃, keeping the temperature for 1 hour, stopping heating, washing the wood fiber by using clear water until the aqueous solution is neutral, and finally drying the wood fiber. Referring to fig. 1, a process diagram of delignification of wood fibers into pure white in example 1 of the present invention is shown, wherein the wood fibers are soaked in an aqueous sodium chlorite solution for 0, 15, 30, 60 and 90 minutes, respectively.

2) As shown in fig. 2, in order to prepare a highly transparent and highly scattering wood-based composite material by a VARI process, air-dried lignocellulose is manually paved into a three-dimensional and uniformly interwoven fiber mesh in a helmet-type mold master die, the male die is closed, an epoxy resin system is permeated into the fiber mesh under high pressure by the VARI process, the resin is cured at 80 ℃ for 2 hours, then cured at 150 ℃ for 2 hours, cooled to room temperature after curing is finished, the mold is removed, and a cured sample is taken out to obtain the highly transparent and highly scattering wood-based composite material, wherein the mass fraction of the wood fiber reaches 85%, and the mass fraction of the resin matrix reaches 15%.

The adopted epoxy resin system is a mixture of E51 epoxy resin monomer and curing agent, the curing agent is polyamide, and the curing agent accounts for 30% of the total mass.

The VARI process comprises coating a release agent on the surface of a helmet female die, uniformly paving a wood fiber net in the die, sequentially paving release cloth, a flow guide net and a plastic film on the fiber net, cutting two small holes at two ends of the plastic film, connecting one small hole with a resin system through a conduit, connecting the other small hole with a vacuum pump through a conduit, sticking and sealing the plastic film and the female die by using an adhesive tape, opening the vacuum pump, injecting an epoxy resin system at a vacuum degree of less than or equal to 0.05MPa and an injection temperature of 35 ℃, automatically introducing resin into the fiber net through the conduit under the action of vacuum, and curing to form a product.

Example 2:

1) soaking 100 g of wood fiber (the fiber diameter is less than or equal to 50 mu m, the fiber with the length of less than or equal to 0.10mm accounts for 80% of the total fiber mass) of poplar into sodium hypochlorite aqueous solution (the sodium hypochlorite mass fraction is 10%), just submerging the fiber in the aqueous solution, raising the temperature of the aqueous solution to 100 ℃, keeping the temperature for 1 hour, stopping heating, cleaning the wood fiber by using clear water until the aqueous solution is neutral, and finally drying the wood fiber.

2) Manually paving the aired lignocellulose in a rectangular mold (100cm multiplied by 30cm multiplied by 2cm) to form a three-dimensional uniformly-interwoven fiber net, closing the male mold, permeating a prepolymer system obtained by polymerizing diphenylmethane diisocyanate and polytetrahydrofuran ether glycol (number average molecular weight 1000) into the network-shaped wood fiber net at high pressure by adopting an HT-RTM (high temperature resin transfer molding) process, curing the resin at 70 ℃ for 5 hours, then curing at 120 ℃ for 2 hours, cooling to room temperature after curing, removing the mold, and taking out a cured sample to obtain the high-transparency high-scattering wood-based composite material. Wherein the mass fraction of the wood fiber reaches 85 percent, and the mass fraction of the resin matrix reaches 15 percent.

A prepolymer system obtained by polymerizing diphenylmethane diisocyanate and polytetrahydrofuran ether glycol (number average molecular weight 1000): reacting diphenylmethane diisocyanate and polytetrahydrofuran ether glycol at 80 ℃ for 1.0h, wherein the mass ratio of the diphenylmethane diisocyanate to the polytetrahydrofuran ether glycol is 50 g: 100 g, then adding a chain extender into the reacted prepolymer, wherein the mass ratio of the reacted prepolymer to the 1, 3-butanediol is 150 g: 9 g, and stirring quickly and uniformly to form a molten polyurethane system. After the wood fiber is infiltrated, a curing treatment is performed.

HT-RTM adopts high pressure RTM injection equipment, firstly, a tank filled with resin is connected with RTM (resin transfer molding) equipment through a conduit, then a fiber mesh is uniformly paved in the RTM equipment, then pressure is applied to the resin tank, polyurethane is injected under the conditions that the injection pressure is not less than 0.8MPa and the injection temperature is 30 ℃ (too high temperature can cause too fast curing and influence injection), the polyurethane is pressed into a machine containing a mold, and the product is obtained after curing and demolding.

The high-transparency high-scattering wood-based composite material prepared in the example was tested for light transmittance, haze, flexural strength, flexural modulus of elasticity, and impact strength.

As shown in fig. 3, a light transmittance graph of the high-transparency high-scattering environment-friendly aldehyde-free wood-based composite material prepared in example 1 shows that the light transmittance of the material is above 85% in the visible light range.

As shown in fig. 4, which is a haze chart of the high-transparency high-scattering environment-friendly aldehyde-free wood-based composite material prepared in example 1, it can be seen that the haze of the material is more than 80% in the visible light range.

As shown in fig. 5, which is a bending strength graph of the high-transparent high-scattering environment-friendly aldehyde-free wood-based composite material prepared in example 1, it can be seen that the bending strength of the material is 46.2 ± 4.5 MPa.

As shown in fig. 6, which is a bending elastic modulus graph of the high-transparent high-scattering environment-friendly aldehyde-free wood-based composite material prepared in example 1, it can be seen that the bending elastic modulus of the material is 2940 ± 50 MPa.

As shown in FIG. 7, which is a graph of the impact strength of the high-transparency high-scattering environment-friendly aldehyde-free wood-based composite material prepared in example 1, it can be seen that the impact strength of the material is 4.2 + -0.3 KJ/m²。

As can be seen from the figure, the material has very good light transmittance which is close to that of the conventional glass, has very high haze, is beneficial to improving light scattering, is applied to preparing lampshades and the like, effectively avoids direct irradiation of light rays and reduces dazzling degree. In addition, the material has good mechanical properties and is suitable for practical application.

According to the invention, the lignin-removed wood fiber and the transparent resin are compounded for the first time, and the high-transparency high-scattering wood-based composite material is prepared through a curing reaction, and can be applied to the field of light illumination. The high-transparency high-scattering wood-based composite material prepared by the method is completely different from the traditional surface scattering material and the traditional bulk scattering material, the novel wood-based composite material disclosed by the invention has good light transmittance and high scattering property, the preparation method is simple and feasible, and a large amount of wood is introduced. The invention not only promotes the green development of the high-scattering material, but also has great promoting effect on the scientific development of the wood.

The above embodiments are only used for illustrating but not limiting the technical solutions of the present invention, and although the above embodiments describe the present invention in detail, those skilled in the art should understand that: modifications and equivalents may be made thereto without departing from the spirit and scope of the invention and any modifications and equivalents may fall within the scope of the claims.

Claims

1. A preparation method of a multi-dimensional special-shaped high-transparency high-scattering environment-friendly aldehyde-free wood-based composite material comprises the following steps: removing lignin from wood fibers, uniformly paving the wood fibers into a three-dimensional fluffy fiber net, putting the three-dimensional fluffy fiber net into a female die of a multi-dimensional special-shaped die, closing a male die, then permeating transparent liquid resin into the wood fibers, and carrying out curing treatment, wherein the resin is a non-polar material, the wood fibers are polar materials, and the interface compatibility between the resin and the wood fibers is poor, so that interface gaps are formed, light is promoted to be seriously scattered in the composite material, and the multi-dimensional special-shaped high-transparency high-scattering wood-based composite material is obtained.

2. The preparation method of the multi-dimensional heterotype high-transparency high-scattering environment-friendly aldehyde-free wood-based composite material according to claim 1, characterized in that: the preparation method comprises the following specific steps:

(1) removing lignin: soaking the wood fiber in an aqueous solution of sodium hypochlorite, sodium chlorite or a mixture of the sodium hypochlorite and the sodium chlorite, raising the temperature of the aqueous solution to 70-100 ℃, stopping heating when the mass content of lignin in the wood fiber is less than or equal to 10%, cleaning the wood fiber by using clear water until the aqueous solution is neutral, and finally drying the wood fiber; the diameter of the wood fiber is less than or equal to 50 mu m, and the length of the wood fiber is less than or equal to 2 mm;

(3) resin infiltration: and (2) permeating the resin into the fiber web by adopting a VARTM (vacuum assisted resin transfer molding) or HT-RTM (high pressure resin transfer molding) or VARI (vacuum assisted molding) process, curing the resin at the temperature of between 20 and 200 ℃ until the curing reaction is finished, removing the mold, and taking out a cured sample to obtain the high-transparency high-scattering composite material.

3. The preparation method of the multi-dimensional profiled high-transparency high-scattering environment-friendly aldehyde-free wood-based composite material according to claim 2, characterized in that: the wood fiber with the length less than or equal to 0.15mm accounts for more than 60 percent of the total fiber mass fraction.

4. The preparation method of the multi-dimensional profiled high-transparency high-scattering environment-friendly aldehyde-free wood-based composite material according to claim 2, characterized in that: when the lignin is removed, the heating time is 10min-5h, based on the condition that the wood fiber is just submerged by sodium hypochlorite, sodium chlorite or a mixed aqueous solution of the sodium hypochlorite and the sodium chlorite in a container; the mass fraction of the sodium hypochlorite, the sodium chlorite or the mixture of the sodium hypochlorite and the sodium chlorite in the aqueous solution is 1 to 15 percent.

5. The preparation method of the multi-dimensional profiled high-transparency high-scattering environment-friendly aldehyde-free wood-based composite material according to claim 2, characterized in that: the paving is manual paving, airflow paving or carding machine paving, and a three-dimensional fluffy network shape is formed.

6. The preparation method of the multi-dimensional profiled high-transparency high-scattering environment-friendly aldehyde-free wood-based composite material according to claim 2, characterized in that: the multi-dimensional special-shaped mould comprises a square block type mould, a rectangular block type mould, a helmet type mould, a lampshade type mould and a hemispherical mould.

7. The preparation method of the multi-dimensional profiled high-transparency high-scattering environment-friendly aldehyde-free wood-based composite material according to claim 2, characterized in that: the resin is an epoxy resin system, polymethyl methacrylate or polyurethane; in the permeation process, the viscosity of the resin is less than or equal to 10Pa · s.

8. The preparation method of the multi-dimensional profiled high-transparency high-scattering environment-friendly aldehyde-free wood-based composite material according to claim 7, characterized in that: the epoxy resin system is a mixture of epoxy resin monomers and a curing agent, the curing agent is polyamide, anhydride, diamine or polyamine substances, and the curing agent accounts for 5-40% of the total mass; the curing temperature is 20-200 ℃, and the light transmittance after curing is more than or equal to 85 percent;

the curing temperature of the polymethyl methacrylate is 50-100 ℃, and the transmittance after curing is more than or equal to 85 percent;

the polyurethane is obtained by carrying out polymerization reaction on raw materials of isocyanate, a polyglycol compound B and a chain extender, wherein the mass of the isocyanate and the chain extender accounts for less than 40% of the mass of the total polyurethane; the isocyanate is any one of diphenylmethane diisocyanate, isophorone diisocyanate and hexamethylene diisocyanate; the polyglycol compound B is any one of polytetrahydrofuran ether glycol, polyoxyethylene glycol, polytetrahydrofuran-ethylene oxide glycol and polyoxypropylene glycol, and the number average molecular weight is between 500-1500; the chain extender is 1, 4-butanediol, 1, 3-butanediol or a mixture of the two; the curing temperature of the polyurethane is 50-150 ℃, and the transmittance after curing is more than or equal to 85%.

9. The preparation method of the multi-dimensional profiled high-transparency high-scattering environment-friendly aldehyde-free wood-based composite material according to claim 2, characterized in that: adopting VARTM, HT-RTM or VARI process to make resin completely permeate into wood fiber network, and making internal porosity of the composite material after forming less than or equal to 1%; the VA-RTM is resin injected at the vacuum degree of less than or equal to 0.05MPa and the injection temperature of 20-50 ℃; the HT-RTM is resin injected under the injection pressure of more than or equal to 0.8MPa and the injection temperature of 20-50 ℃; the VARI is resin injected under the vacuum degree of less than or equal to 0.05MPa and the injection temperature of 20-40 ℃.

10. The preparation method of the multi-dimensional profiled high-transparency high-scattering environment-friendly aldehyde-free wood-based composite material according to claim 2, characterized in that: in the composite material, the mass fraction of the wood fiber is 75-90%, and the mass fraction of the resin is 10-25%.